Xueming Hong

Some features of the photonic crystal fiber temperature sensor with liquid ethanol filling.

We introduce a novel photonic crystal fiber (PCF) temperature sensor that is based on intensity modulation and liquid ethanol filling of air holes with index-guiding PCF. The mode field, the effective refractive index and the confinement loss of PCF were all found to become highly temperature-dependent when the thermo-optic coefficient of the liquid ethanol used is higher than that of silicon dioxide and this temperature dependence is an increasing function of the d/Lambda ratio and the input wavelength. All the experiments and simulations are discussed in this paper and the temperature sensitivity of transmission power was experimentally determined to be 0.315 dB/ degrees C for a 10-cm long PCF.

Compact and Ultrasensitive Temperature Sensor With a Fully Liquid-Filled Photonic Crystal Fiber Mach–Zehnder Interferometer

We propose a compact and ultrasensitive all-fiber temperature sensor based on an in-line fully liquid-filled photonic crystal fiber (PCF) Mach-Zehnder interferometer (MZI). It consists of a small piece of index-guiding PCF fully infiltrated by fluid and two standard single-mode fibers offset spliced with PCF. Two core modes LP01 and LP11 are conveniently used as optical arms to form the in-line MZI-type interferometer. Experimental and theoretical investigations of its response to temperature confirm that high temperature sensitivity up to -1.83 nm/°C could be realized with such a compact interferometeric PCF temperature sensor.

Experimental realization of D-shaped photonic crystal fiber SPR sensor

A novel surface plasmon resonance sensor based on a D-shaped, all-glass, endless single-mode photonic crystal fiber is experimentally demonstrated in this paper, which provides a new approach to realizing a high-performance photonic crystal fiber surface plasmon resonance sensor. In order to achieve the best performance, the side-polished position of the D-shaped photonic crystal fiber is theoretically and experimentally obtained. The proposed sensor can be used in wavelength and intensity interrogations simultaneously, and the experimental results of wavelength interrogation agree well with theoretical results. By combining the two interrogation methods, we present a two-feature interrogation method to improve the resolution. As a new interrogation method, the two-feature resolution is determined to be 6.53 × 10−5 RIU, which is higher than those of the wavelength and intensity interrogations.

Angular characteristics of a multimode fibre surface plasmon resonance sensor under wavelength interrogation

In this paper the angular characteristics of a multimode fiber SPR sensor are theoretically investigated. By separating the contributions of beams incident at different angles, a compact model is presented to predict the shift of the resonance wavelength with respect to the angle and the environmental refractive index. The result suggests that the performance of conventional fiber SPR sensors can be substantially improved by optimizing the incident angle. Furthermore, our investigation suggests some problems in previous reports.

A label-free fiber optic SPR biosensor for specific detection of C-reactive protein

A highly sensitive and label-free fiber optic surface plasmon resonance (SPR) biosensor for specific detection of C-reactive protein (CRP) is proposed and demonstrated. We take dopamine as a cross-linking agent to immobilize the anti-CRP monoclonal antibody, which is an efficient and simple method for specific modification of the fiber optic SPR sensor. The modified sensor can successfully detect CRP specifically. We realize the fabrication of a disposable fiber optic SPR sensor for the CRP specific detection. Through optimizing the immobilization time of anti-CRP monoclonal antibody and the reaction time of antigen and antibody experimentally, the sensor shows a satisfactory linear response (R2 = 0.97) to CRP concentration within the range from 0.01 to 20 μg/ml. Moreover, the highest CRP sensitivity is obtained at 1.17 nm per lg (μg/ml). With the advantages of simple structure and easy fabrication, our sensor is convenient to be batch produced and controlled with good consistency, which is especially suitable for the fabrication of disposable biosensor. It makes sense that our detection can effectively avoid the cross pollution caused by repeated use of the sensor.

Refractive index detection range adjustable liquid-core fiber optic sensor based on surface plasmon resonance and a nano-porous silica coating

A liquid-core fiber optic surface plasmon resonance sensor with an adjustable nano-porous silica coating is first presented in this paper. By adjusting the refractive index of the nano-porous silica coating, the sensor can be used in different refractive index detection ranges. A low refractive index interval of 1.33–1.34 and a high refractive index interval of 1.42–1.44 are taken as examples to be investigated. Results show that our sensor works well in these two intervals by using appropriate nano-porous silica coatings. The highest sensitivities of the low and high refractive index intervals are obtained to be 5840 nm/RIU and 5120 nm/RIU, respectively. In addition, the sensing performances and the working wavelengths can be adjusted to meet different working requirements by changing the refractive index of the nano-porous silica coating. We also take the single mode incidence cases to explain the effects of different single incident light modes on the sensing performances.

Realization of All-in-Fiber Liquid-Core Microstructured Optical Fiber

We present an approach for manufacturing liquid-core microstructured optical fiber (MOF) with an all-in-fiber configuration. The MOF is first fusion-spliced with conventional fiber pigtails, with channels left open at the spliced interfaces to allow filling. After liquid filling, the channels are sealed by adhesives to prevent evaporation of the liquid. To verify the efficacy of this method, we filled a simplified hollow-core MOF (SHC-MOF) with a solution of aqueous quantum dots, and the temperature characteristics of the filled SHC-MOF were measured. The fluorescent peak wavelength and intensity changed reversibly over 48 h of repeated temperature cycling, indicating that the all-in-fiber configuration of the integrated liquid-core SHC-MOF has long-term stability and that the evaporation of the filling solution is minimal.

All-fiber reflecting temperature probe based on the simplified hollow-core photonic crystal fiber filled with aqueous quantum dot solution.

An all-fiber reflecting fluorescent temperature probe is proposed based on the simplified hollow-core photonic crystal fiber (SHC-PCF) filled with an aqueous CdSe/ZnS quantum dot solution. SHC-PCF is an excellent PCF used to fill liquid materials, which has low loss transmission bands in the visible wavelength range and enlarged core sizes. Both end faces of the SHC-PCF were spliced with multimode fiber after filling in order to generate a more stable and robust waveguide structure. The obtained temperature sensitivity dependence of the emission wavelength and the self-referenced intensity are 126.23 pm/°C and -0.007/°C in the temperature range of -10°C-120°C, respectively.

Quantum Dots-Based Multiplexed Fiber-Optic Temperature Sensors

Quantum dots (QDs)-based multiplexed fiber-optic temperature sensors are proposed for multi-point sensing, which are composed of hollow-core microstructured optical fibers filled with aqueous QDs solutions of different fluorescent wavelengths. A parallel reflective configuration is adopted to avoid the crosstalk of fluorescent emissions, and to construct practical probes. Temperature experiments show that the fluorescent peak wavelength and the self-referenced intensity of two sensors both change with temperature linearly in the range from -10 °C to 120 °C with favorable reversibility. At last, the crosstalk of both the fluorescent peak wavelength and the self-referenced intensity of two sensors is tested for in the range of the temperature measurements.

Sensitivity-Enhanced U-Shaped Fiber SERS Probe With Photoreduced Silver Nanoparticles

This paper presents a novel U-shaped fiber surface-enhanced Raman scattering (SERS) spectra probe with high-performance remote sensing based on femtosecond laser ablation and deposition of photoreduced silver nanoparticles. As the width of the U-shaped structure is around 12 μm, the sensitivity is enhanced about four times more than that of a single-endface-based fiber SERS probe. The experiment results show that there is a nonlinear relationship between the SERS signal and the width of the U-shaped structure, whereas the SERS signal is sharply decreased with the increasing width of the U-shape. Our U-shaped fiber SERS probe shows a feasible method for high-performance, real-time, and remote measurement of the SERS signal in biochemical analysis.